Removal of solid phases, and especially removal of scum and flocculated materials from aqueous fluids has been practiced in numerous industries for several decades. However, despite the technically relatively simple task, numerous difficulties remain.
For example, centrifugal separation provides a relatively effective and fast method of separating a solid phase from a liquid, however, has limited use where the particle size and/or concentration are relatively low. Moreover, and especially where the volume of treated fluid is relatively large, centrifugal separation often becomes impractical due to the required rotor size and energy consumption. Alternatively, lamella-type separators can be employed that obviate the need for moving parts. Such separators are often relatively energy efficient and typically allow for a good separation efficacy. However, centrifugation and lamella-type separation are generally only effective for solid materials that have a higher density than the solvent (typically water).
Where the solid material has a lower density than the solvent (e.g., sticky & non sticky-oil sludge, scum, and/or coagulated-flocculated materials) solids can often easily removed without significant mechanical intervention in settling or holding tanks to allow density separation. However, where the effluent volume is relatively large and/or the density difference is relatively small, required volumes for the settling or holding tanks and time for separation would be impractical under most circumstances. To speed up separation, mechanical measures can be taken. For example, many of the currently operating separators employ dissolved air flotation or impart centrifugal momentum into the mixed-phase feed. While such approaches are conceptually relatively simple, currently known separators often require moving parts and significant amounts of energy. Moreover, moving parts require maintenance and therefore add further cost and/or downtime. To overcome at least some of these difficulties, gas liquid coalescers (e.g., U.S. Pat. No. 5,156,745) using microscopic gas bubbles may be employed in which the device is configured to reduce inter cell or vessel chamber turbulence to reduce or even eliminate remixing of the separated material with the fluid. While such device advantageously reduces at least in some cases energy consumption and improves separation efficiency, several disadvantages still remain. For example, as the solution moves through the gas liquid coalescer in a single pass, high efficiency must be maintained at all times to produce a consistently clarified product.
Therefore, while numerous methods of mixed-phase separation are known in the art, all or almost all of them suffer from one or more disadvantages. Consequently, there is still a need to provide improved configurations and methods to improve mixed-phase separation, especially where colloidal clay/silica etc. are emulsified in a liquid.